What is a receiver drier?

By Richard Hawkins, MACS contributor

A MACS blog article dated October 13, 2010, begins with the following sentence:  “For reasons we just can’t figure out the number one internet search for mobile A/C components and the number one blog post consistently read is about the function of the system’s receiver drier.” To read that blog article, please go to the following link: https://macsmobileairclimate.org/2010/10/13/what-is-a-receiver-drier/      

Also, here is another blog article which contains some excellent information on receiver driers and accumulators too:  https://macsmobileairclimate.org/2010/07/13/three-important-functions-of-the-receiverdrier-in-your-cars-ac-system/

Both articles serve as a good review on receiver drier and accumulator function.

In March 2022 that same sentence from the October 2010 blog article holds true. Now with A/C season just around the corner, this seems like a good time to provide some updated information on these units. 

NOTE:  Receiver driers are sometimes called filter driers and accumulators are sometimes called accumulator driers.

First, we will observe the similarity of the two units:

• Receiver driers and accumulators both dry (absorb moisture) from refrigerant. This is accomplished by desiccant which is contained in the units. Please see pictures #1 and #2.

Picture #1:  Two slightly different designs of receiver driers. The one on the left utilizes desiccant bags. The one on the right has the desiccant sandwiched between an upper and lower plate which have holes in them to allow refrigerant to flow through.  The opening for the pickup tube for the unit on the left is covered by a filter which prevents debris from getting to the expansion valve. The filter for the unit on the right is located directly above the desiccant.

• Receiver driers and accumulators both store reserve refrigerant. All A/C systems are designed to hold some refrigerant in reserve to compensate for normal refrigerant loss.  

• Receiver driers and accumulators both function as liquid/vapor separators. However the result of this function is exactly opposite of one another.  A receiver drier is designed to prevent vapor from flowing out of it into the liquid line that runs to the expansion valve. An accumulator is designed to allow only vapor to flow from it into the suction line that runs to the compressor. These functional characteristics are accomplished by the positioning of the pickup tubes inside of the units.

The pickup tube for the refrigerant in a receiver drier extends downward toward the bottom of the unit and the opening in the tube is at the very bottom. Liquid is heavier than vapor,  so liquid will be in the bottom of the receiver drier and will be introduced into the pickup tube.   Vapor is lighter than liquid, so any vapor that is introduced will be in the top part of the unit above the liquid. Please see picture #1.

An accumulator has the pick-up tube for the refrigerant extending upward. The opening in the pick-up tube for the refrigerant is at the very top. With liquid refrigerant boiling off in the lower portion of the unit and lighter vapor being in the top, this ensures that only vapor will enter the pickup tube and will exit the accumulator.  Please see picture #2.

• Receiver driers and accumulators both filter refrigerant oil. Please see pictures #1 and #2.

Picture #2: Three slightly different designs of accumulators. The one of the left has a trumpet shape on the pickup tube and it extends almost to the top of the unit. This is to prevent liquid refrigerant, which is flowing in from the inlet, from getting into the pickup tube. The units in the center and on the right utilize baffles to protect the pickup tube from liquid refrigerant.  There is a .040 diameter hole drilled in the bottom of the pickup tubes.  This is there to allow oil to flow into the tubes where it is picked up by refrigerant.  It is then carried into the suction line and on to the compressor.  Screens are placed over the oil bleed holes to filter out debris.
 Photo credit : Cool Air Automotive 

Now we will observe the differences in the two units:

• Receiver driers are located on the high side of an A/C system.

• Accumulators are located on the low side of an A/C system.

• Receiver driers filter refrigerant.

• Accumulators do not filter refrigerant.  Orifice tube systems use accumulators and the screen on the orifice tube is the filter for the refrigerant.

Check back in next week and we will dig further into receiver drier and accumulator function and the need to replace them when performing A/C service work.

Join MACS and become part of a like-minded group of professionals working hard on cooling what moves you.